For Reducer 2’s "Reduce Vectorization:" you’ll see "groupByVectorOutput:": "false" which says a node has a GROUP BY with an AVG or some other aggregator that outputs a non-PRIMITIVE type (e.g. STRUCT) and all downstream operators are row-mode. I.e. not vector output.

If "usesVectorUDFAdaptor:": "false" were true, it would say there was at least one vectorized expression is using VectorUDFAdaptor.

And, "allNative:": "false" will be true when all operators are native. Today, GROUP BY and FILE SINK are not native. MAP JOIN and REDUCE SINK are conditionally native. FILTER and SELECT are native.